THE SPINE. 81 



of the spine. Their bodies and processes are small, but the 

 spinal foramen is large, so as to admit of much motion, without 

 pressing on the spinal marrow. The fore and back parts of the 

 body are more flattened. The upper face is concave transverse- 

 ly, being bounded on each side by a ridge of bone; the lower 

 face is concave from before backwards, and is bounded by a 

 ridge before and behind. This arrangement permits the bodies 

 of adjoining vertebrae to embrace each other in the dried bones, 

 and grants great facility of motion, in the living body, by the 

 interposition of the intervertebral substance, as well as securi- 

 ty in the attachment of the latter. 



The oblique processes have their articular faces at an angle 

 of about forty-five degrees. The superior face upwards and 

 backwards, the inferior downwards and forwards. The spinous 

 process is short, triangular, nearly horizontal, and bifurcated at 

 its posterior extremity, where it terminates in two tubercles. 

 The transverse processes are short, and perforated by a large 

 canal for the transmission of the vertebral artery and vein ; they 

 are concave above, somewhat convex below, and present two 

 points at their external extremities for the origin and insertion 

 of muscles. The inter- vertebral foramen is formed principally 

 by the lower of the contiguous vertebrae. 



Of the Cervical Vertebra, individually. 



The first cervical vertebra, commonly called the Atlas, from 

 its supporting the head, presents the appearance of a large ir- 

 regular ring, much thicker at its sides than elsewhere. It is 

 deficient in body, owing to the space allotted to that part in the 

 other vertebrae being occupied by the processus dentatus of the 

 second vertebra. The place of body is supplied by an arch of 

 bone. 



Its oblique processes are peculiar, both in shape and position. 

 The upper ones are concave and horizontal, their long diameters 

 being extended from within outwards and backwards, so as to 

 suit the direction of the condyles of the occipital bone with 

 which they articulate; the greatest depth of their concavity is, 

 therefore, internal. The inferior oblique processes are smaller, 

 slightly concave, and circular; they rest upon the shoulders of 

 the second vertebra. At the internal margin of the oblique pro- 



